In the CEATEC Japan 2009 exhibition hold in Makuhari Messe, lots of exhibitors, such as Panasonic, Sharp, and TDK, showed a new concept about “DC supplying room” which supply DC source to electronics equipment instead of conventional AC source. The advantage of DC powering is to reduce the carbon emission effectively. Nowadays, the power consumption of the IT equipments is increased rapidly, the global total power consumption of IT equipments of 2025 will increase to 9.4 times of 2006, and it occupied 15% of the global generated power. For Japan only, the total power consumption of IT equipments will be 5.2 times of the power consumption of 2006, and it occupied 20% of Japan's generated power. If the power system of the IT equipment can be changed from AC supplying system to DC supplying system, the power consumption of the IT equipment can reduce 10%˜20%.
In addition, in order to prevent the power shut down, most of the data centers equipped uninterruptible power supply (UPS). Thus, the AC power comes from the power network will be converted to DC power by an AC/DC converter and the DC power will be stored into a power storage apparatus. Then, the stored DC power will be converted to AC power before provide to the IT equipment, such as a server. After that, the power apparatus of the server will convert the received AC power into DC power and provides it to the equipment. In other words, the power sent from the power network will be AC/DC converted at least 3 times before it powering the equipment. The power loss caused from the power conversion is around 27% after three times conversions even the efficient of power conversion is as high as 90%. Thus, if we can DC powering the equipment directly, the power lose of the power conversion can reduce dramatically to decrease the power consumption further to reduce the carbon emission.
Nikkei Electronics and the environmental and energy department of NPO held a seminar about the trend of photovoltaic, lithium ion battery, and DC powering on Oct. 21, 2010. During this seminar, the chairman of the advance technology development department has a speech about the develop tendency of DC wiring system and the smart-housing based on the Home Energy Management Systems (HEMS). In addition, on the 2010 CEATEC exhibition, Panasonic and Sony show a concept to integrate the battery and the DC power. Wherein, Panasonic disclosed a new generation of the distribution panel called “Smart Energy Gateway” (SEG) which combines the solar cell and the battery. SEG can provide the DC power and also the AC power. The SEG distribution panel can control the power consumption of each electronic device, light apparatus in your house and execute the management function to manage all electronic devices. Sony displayed how the DC power, which stored in the phospho-olivine energy storage module, drives the LCD TV. The capacity of the phospho-olivine energy storage module is 1.2 KWH which is capable to support the AC and DC outputs.
FIG. 1 illustrates a conventional structure of extension cord. Due to the domestic power source is single phase currently, the conventional extension cord includes a conducting line (live wire) which used to transfer the AC power, and the live wire and another conducting line (neutral line) form a loop. Most of plugs and sockets further configured a third slot for connecting to an earth line for grounded the equipment in order to avoid the leakage damage. However, the aforementioned structure of the extension cord can only applied in the AC input and AC output system.